There are many different types of documents issued by government agencies, corporations and individuals that authorize the holder of such documents to perform authorized tasks or grant rights to the holder of such a document. Examples of such documents are drivers' licenses, passports, entry access badges, identification cards, tickets, gift certificates, coupons, bonds, postal indicia, and the like.
With the advent of computers and refined printers that are available at a relatively low cost, the incidence of forgery of the above types of documents has proliferated. Although there are processes that apply coatings to documents to prevent copying, this does not end the problem of forgery.
Various schemes have been proposed to provide security to issued documents to inhibit forgeries of such documents. One such scheme is to use encryption so that a code can be derived that is based upon the information on the face of the issued document. Unfortunately, because of the limited space normally available in such documents, such a scheme often proves impractical.
The issuance of many types of tickets, such as theater tickets, is currently controlled by means of controlled supplies (e.g., serialized ticket stock, specially printed ticket stock, etc.) and by allowing tickets to be issued only by controlled, authorized issuers (e.g., ticket agents). Controlled supplies are expensive, difficult to control, and prone to theft or counterfeiting. Typically, one stood in line to purchase a ticket at the place the event was being held or purchased the ticket over the phone from an authorized ticket agent who mailed the ticket to the purchaser.
Currently, ticketing companies are giving purchasers the option of printing their electronic tickets at home using ordinary paper, a personal computer printer and an Internet connection. One of the problems in allowing people to print tickets at home is how to ensure that the tickets are not counterfeited. Furthermore, the printing technology used is another major factor, specifically when combined with the type of paper the ticket is printed on.
Unfortunately, if a ticket is printed properly on ordinary paper with an encrypted bar code, the ticket can be photocopied, and the seller of the ticket will be unable to distinguish between the original real ticket and the photocopied ticket.